The longtime DJ at a popular Buckhead nightclub is battling an aggressive form of cancer, and friends and fans want to help.

For 21 years, Jack “DJ Happy Jack” Pena has kept people on their feet at Johnny’s Hideaway on Roswell Road.

Not long ago, though, Pena, 58, who lives in Canton, was diagnosed with late-stage lower esophageal cancer, which has metastasized to his liver.

On Thursday, Johnny’s Hideaway will donate 20% of sales to Pena, who doesn’t have health insurance.

Pena, who recently underwent his third round of chemotherapy, is on medical leave from his job. He’s not sure when he will return.

“My greatest worries are my wife and children,” said Pena, who said deejaying has been his life’s work. “I want them to be OK. I’m grateful that people care enough to want to do something, but it’s kind of embarrassing, to be honest. I never pictured myself as being the subject of a fundraiser, but I can’t work anymore and that’s ended up changing everything in our lives.”

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The fundraiser is the brainchild of Johnny’s Hideaway owner Chris Dauria, who wanted to show his appreciation for the man behind the hip-shaking music at the nightspot.

“It’s incredible the way he turns the dance floor,” Dauria said. “Everything he does is so good, so professional.”

Separately, Pena has started a GoFundMe page to raise money to help cover expenses for his family.

So far, he’s raised nearly $12,000 toward the $100,000 goal.

Pena’s salary was the sole income for his family. Now, unless things change, they may have to sell their home and move in with one of his sisters in Florida.

His wife, Nisha, had to quit her job a few years ago to become a full-time caregiver to their teenage son, who has autism. The couple also have two adult sons.

Their youngest son is nonverbal. “He will not have a job and will live with us forever, which kind of makes my situation even more upsetting,” said Pena, a graduate of Marietta High School.

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Pena said some bills have totaled as much as $26,000 at one time, and he’s been unable to afford premiums for the Affordable Care Act, which he called “a joke.”

He’s gotten help from special funds from health care providers.

Indeed, cancer patients can face staggering financial problems associated with their out-of-pocket care and, often, their inability to work or because they lack adequate health insurance — if they have any.

“Financial toxicity” is a term that has been used in the medical community and among cancer nonprofits to describe issues a patient may have related to their medical care, according to the National Cancer Institute.

Lack of money can force a patient to forgo doctor’s visits or ability to buy medicine. It can also lead to debt and bankruptcy.

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“If you go to the doctor, it’s money. If you go to the hospital, it’s money. You get this test or that test. Everything costs money,” Pena said. “If you’re fortunate enough to have health insurance, you don’t get to see that gigantic whole bill. It’s ugly.”

Pena watched his mother die of pancreatic cancer, a particularly deadly cancer that is often not diagnosed until it is far advanced.

For Pena, the first sign that something was wrong was when he started having problems eating.

It might take him as long as an hour to eat a meal, and he experienced extreme discomfort.

“It was so hard to get food down,” he said. “I didn’t know why I couldn’t eat normal anymore.”

To get nourishment, he would forgo solid foods for liquid meal supplements or smoothies.

What he didn’t realize was that a tumor was creating a blockage.

The news wasn’t good. The cancer was advanced.

He said doctors have given him his “sentence.” He said he has stage 4 cancer. “They have given me 14 to 18 months. If I get a miracle, I might make it three years.”

“You think about everything,” he said. “You think about dying. I’ve always been a Christian. I guess I’ll find out if my beliefs are true.”